[RESOLVED] Keeping track of ellipses

[dkdsmk]

Suppose i want to draw semi-random ellipses on my form.

Is there any way i can check if they get clicked at a later stage?

Is there any way of storing the location of individual ellipses and then comparing the mouse-click to my list of locations to see if one was clicked?

I can imagine how it could be done with squares or rectangles, but i dont know how to approach it with ellipses.

Im sure this has been asked before, but i've spent a good while searching around for something i can use and came up emptyhanded.

Thanks a bunch!

[.paul.]

you'd store the rectangle bounds of the ellipse, in a list(of rectangle). then you'd use a mathematical formula to check if the mouseclick was within the ellipse, within it's bounding rectangle.

i don't know the formula you'd use though. try asking in the math forum

[dkdsmk]

Yes, i figured it was something like that. I guess its the easiest way ^^
We'll see if its beyond my abilities or not. Gonna go hunt for that formula. Thanks alot! ^^

[Negative0]

It's actually pretty easy to figure out if the point is contained in rectangle. Something like this:

    Dim allEllipses As List(Of Rectangle)
    Dim rand As New Random()
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        allEllipses = New List(Of Rectangle)
        Using g As Graphics = Graphics.FromHwnd(Me.Handle)

            For i = 1 To 5

                Dim s As SizeF = g.MeasureString("...", Me.Font)
                Dim p As Point = New Point(rand.Next(0, Me.Width), rand.Next(0, Me.Height))
                g.DrawString("...", Me.Font, Brushes.Red, p)
                Dim r As New Rectangle(p, s.ToSize())
                allEllipses.Add(r)
            Next
        End Using

    End Sub

    Private Sub Form1_MouseClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseClick
        For Each r As Rectangle In allEllipses
            If r.Contains(e.Location) Then
                MessageBox.Show("Clicked")
            End If
        Next
    End Sub

[.paul.]

i thought of a different method, using a hidden picturebox:

Public Class Form1
 
    Dim boundingRectangles() As Rectangle
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        boundingRectangles = New Rectangle() {New Rectangle(20, 20, 100, 100), New Rectangle(50, 50, 200, 200)}
    End Sub
 
    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        For Each r As Rectangle In boundingRectangles
            If r.Contains(e.Location) Then
                Dim pb As New PictureBox
                pb.Bounds = r
                Dim r2 As Rectangle = r
                r2.Offset(-r2.Left, -r2.Top)
                Dim path As New Drawing.Drawing2D.GraphicsPath
                path.AddEllipse(r2)
                pb.Region = New Region(path)
                Dim p As Point = e.Location
                p.Offset(-r.Left, -r.Top)
                If pb.Region.IsVisible(p) Then
                    MsgBox("point in ellipse " & Array.IndexOf(boundingRectangles, r))
                End If
                pb.Dispose()
            End If
        Next
    End Sub
 
    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        For Each r As Rectangle In boundingRectangles
            e.Graphics.DrawEllipse(Pens.Black, r)
        Next
    End Sub
    
End Class

[dkdsmk]

Let me just say that i am impressed with what you guys can do with a little time on their hands (and i mean little), hehe.

I deeply appreciate it! I will study it and see if i can figure it out ^^